“Recent developments in genetics and molecular biology have classified breast cancer into subtypes based on tumor markers of estrogen (ER), progesterone (PR) and human epidermal growth Factor-2 receptors (Her-2), with the basal-like (ER−, PR−, Her2−) subtype commonly referred to as ‘triple negative’ breast cancer (TNBC) being the most aggressive. Prior studies show that higher socioeconomic status (SES) is associated with increased breast cancer risk, likely due to hormone related risk factors such as low parity and hormonal contraceptive use. However, it is unclear if the relationship between SES and overall breast cancer incidence exists within each subtype, and if this association varies by race/ethnicity,” writes Dr. Tomi Akinyemiju, assistant professor in the department of epidemiology at the University of Alabama at Birmingham School of Public Health, in a recent study conducted in association with department colleague associate professor Dr. John W. Waterbor, as well as associate professor Dr. Maria Pisu, in UAB’s division of preventive medicine.
[Photo: Dr. Tomi Akinyemiju]
The researchers analyzed data from the Surveillance, Epidemiology, and End Results (SEER) Program database (providing information on cancer incidence and survival rates) linked to 2008–2012 American Community Survey data. The analysis was restricted to women diagnosed with breast cancer in 2010, and based on the National Cancer Institute’s SES index—a composite measure of income, employment, occupational class, education, and house value.
According to Dr. Akinyemiju, “Age-adjusted incidence rate ratios were calculated comparing the highest to lowest SES groups by subtype, separately for each race/ethnic group. We identified 47,586 women with breast cancer diagnosed in 2010. The majority was diagnosed with Her2−/HR+ tumors (73 percent), while 12 percent had TNBC.” The authors observed that higher SES was associated with a 32 to 46 percent higher incidence of HR+ breast cancers, specifically HR+/Her2- (IRR Highest vs. Lowest SES: 1.32, 95 percent confidence interval [CI] 1.27–1.39; p value trend: 0.01) and Her2+/HR+ tumors (IRR Highest vs. Lowest SES: 1.46, 95 % CI 1.27–1.68; p value trend: 0.01) among White women. However, there was no association observed between SES and incidence of HR− subtypes (Her2+/HR− or TNBC). “Similar associations were observed among Black, Hispanic, and Asian or Pacific Islander cases,” notes Dr. Akinyemiju. She concludes that “[t]he positive association between SES and breast cancer incidence is primarily driven by hormone receptor positive tumors.”
The team advises that future studies are needed to identify etiologic risk factors for other breast cancer subtypes.
“Socioeconomic Status and Incidence of Breast Cancer by Hormone Receptor Subtype” was published in September in the journal SpringerPlus.
Journal article: http://www.springerplus.com/content/4/1/508/